Field of the Invention
The embodiments of the present invention relate to an organic light emitting display panel and a method of manufacturing the same, and particularly, to an organic light emitting display panel including a low temperature poly silicon (LTPS) thin film transistor (TFT) and a method of manufacturing the same.
Discussion of the Related Art
As times have progressed toward the information-oriented society, flat panel display (FPD) devices which have desired characteristics such as thinness, lightness, and low consumption power are increasing in importance. Examples of the FPD devices include liquid crystal display (LCD) devices, plasma display panels (PDPs), organic light emitting display devices, etc. Recently, electrophoretic display (EPD) devices are being widely used as one type of the FPD device.
In the FDP devices, organic light emitting display devices including a thin film transistor (TFT) use a self-emitting device and have low power consumption, a fast response time, high emission efficiency, high luminance, and a wide viewing angle. Therefore, the organic light emitting display devices are attracting much attention as next-generation FPD devices.
Particularly, an LTPS TFT may be manufactured at a low temperature. In comparison with an amorphous silicon (a-Si) TFT, the LTPS TFT has a high mobility of an electron or a hole, and because it is possible to implement a complementary metal-oxide semiconductor (CMOS) transistor including an N channel and a P channel, the LTPS TFT may be applied to a large-size substrate.
FIG. 1 is a cross-sectional view for describing an active layer of a related art LTPS TFT.
As illustrated in FIG. 1, an organic light emitting display panel including the related art LTPS TFT includes a buffer 11 formed on a substrate 10, an active layer 13 formed on the buffer 11, a gate insulation layer 14 formed on the active layer 13, a gate electrode (not shown) formed on the gate insulation layer 14, an interlayer dielectric (not shown) formed on the gate electrode (not shown), first and second electrodes (not shown) formed on the interlayer dielectric (not shown), and an organic light emitting diode (OLED, not shown) connected to the first electrode or the second electrode.
The active layer 13 of the LTPS TFT is formed on the substrate 10 through a photolithography process using a mask. In this instance, inclined planes 13a and 13b are respectively formed on both sides of the active layer 13 formed on the substrate 10.
When the related art LTPS TFT is driven, a strong electric field is generated from each of the inclined planes 13a and 13b of the active layer 13. As the strong electric field is generated, a free carrier occurs in each of the inclined planes 13a and 13b, and a hump channel where a high current flows even under a low voltage may be formed.
A gate-source voltage (Vgs) which is a difference voltage between a gate and a source is shifted in a negative (−) direction by the hump channel. As the gate-source voltage (Vgs) is shifted in the negative (−) direction, an off-current of a TFT increases.
Moreover, consumption of power of the organic light emitting display panel increases, and for this reason, deterioration of a transistor is accelerated.
Moreover, a reliability of the organic light emitting display panel is degraded.